Polarized exposure for web manufacture

Abstract

A system is provided in which an expanded non-collimated source of light may be used to produce a uniform polarized light exposure for use, for example, in the photo alignment of optical films. Uniformity of polarization and intensity may be maintained even when a high-intensity source of ultraviolet light is used. The system may be scaled in size to produce large exposures without sacrificing uniformity of intensity of uniformity of direction of polarization. The system includes a light source, a pile-of-plates polarizer, and a surface (such as the surface of an optical film) to be exposed. The pile-of-plates polarizer is oriented orthogonally to the surface, thereby providing a polarized light exposure having a uniform direction of polarization on the exposed surface. The light source may be oriented at Brewster's angle to the polarizer to improve polarization contrast.

What is claimed is:  
     
       1. A system comprising: 
       a polarizer comprising at least one polarizing plate, wherein a non-collimated source light beam incident upon the at least one polarizing plate is polarized to develop a polarized light beam; and  
       a surface oriented substantially orthogonally to the plane of the at least one polarizing plate and positioned in the optical path of the polarized light beam, whereby the polarized light beam is incident upon the surface to produce a polarized light exposure having a substantially uniform direction of polarization across the surface.  
     
     
       2. The system of  claim 1 , further comprising a light source to emit the source light beam. 
     
     
       3. The system of  claim 2 , wherein the light source comprises an extended light source. 
     
     
       4. The system of  claim 2 , wherein the at least one polarizing plate is oriented at about Brewster's angle to an axis of the light source. 
     
     
       5. The system of  claim 1 , wherein the source light beam is an ultraviolet light beam. 
     
     
       6. The system of  claim 1 , wherein the polarizer comprises a pile-of-plates polarizer. 
     
     
       7. The system of  claim 6 , wherein the at least one polarizing plate comprises a plurality of polarizing plates. 
     
     
       8. The system of  claim 7 , wherein the plurality of polarizing plates includes a polarizing plate that is closest to the surface, the plane of said polarizing plate closest to the surface being oriented substantially orthogonally to the surface, and wherein at least one of the plurality of polarizing plates that is not closest to the surface is not oriented substantially orthogonally to the surface. 
     
     
       9. The system of  claim 7 , wherein the at least one polarizing plate comprises a single polarizing plate. 
     
     
       10. The system of  claim 1 , wherein the at least one polarizing plate comprises at least one transmissive polarizing plate. 
     
     
       11. The system of  claim 1 , wherein the at least one polarizing plate comprises at least one reflective polarizing plate. 
     
     
       12. The system of  claim 1 , wherein exposure to the polarized beam aligns molecules on the surface in the direction of the polarized beam's plane of polarization. 
     
     
       13. The system of  claim 1 , wherein the surface comprises a surface of an optical film having a coating of Linear PhotoPolymerization material. 
     
     
       14. The system of  claim 13 , wherein the azimuth of the system is defined as the angle between a plane of symmetry of the web, comprising its normal and its direction of travel, and the plane of incidence, comprising the normal to the web and the optical axis of the incident light, and wherein the azimuth is between 0 and 45 degrees. 
     
     
       15. The system of  claim 13 , wherein the azimuth of the system is defined as the angle between a plane of symmetry of the web, comprising its normal and its direction of travel, and the plane of incidence comprising the normal to the web and the optical axis of the incident light, and wherein the azimuth is between 45 and 90 degrees. 
     
     
       16. The system of  claim 1 , wherein the surface comprises a surface of a liquid crystal cell. 
     
     
       17. The system of  claim 1 , further comprising a first lens disposed between the source light beam and the polarizer. 
     
     
       18. The system of  claim 1 , wherein the surface comprises a virtual surface that is an image formed by an optical element of a real surface. 
     
     
       19. The system of  claim 18 , wherein the optical element comprises a mirror. 
     
     
       20. The system of  claim 18 , wherein the surface is parallel to an axis of symmetry of the system. 
     
     
       21. The system of  claim 1 , wherein the angle between the at least one polarizing plate and a normal to the surface is between −5 and +5 degrees. 
     
     
       22. A system comprising: 
       an extended light source to emit a non-collimated source light beam;  
       a pile-of-plates polarizer comprising at least one transmissive polarizing plate disposed in an optical path of the source light beam to develop a polarized light beam; and  
       a surface oriented substantially orthogonally to the plane of the at least one polarizing plate and positioned in the optical path of the polarized light beam, whereby the polarized light beam is incident upon the surface to produce a polarized light exposure having a substantially uniform direction of polarization across the surface, and wherein exposure to the polarized beam aligns molecules on the surface in the direction of the polarized beam's plane of polarization.  
     
     
       23. The system of  claim 22 , wherein the at least one polarizing plate is oriented at about Brewster's angle to an axis of the light source. 
     
     
       24. The system of  claim 22 , wherein the source light beam is an ultraviolet light beam. 
     
     
       25. The system of  claim 22 , wherein the surface comprises a surface of an optical film having a coating of Linear PhotoPolymerization material. 
     
     
       26. The system of  claim 22 , wherein the surface comprises a surface of a liquid crystal cell. 
     
     
       27. In a system comprising a polarizer including at least one polarizing plate, a method comprising steps of: 
       (A) developing a polarized light beam by providing a non-collimated source light beam to the at least one polarizing plate; and  
       (B) positioning a surface in the optical path of the polarized light beam, wherein the surface is oriented substantially orthogonally to the plane of the at least one polarizing plate, and whereby the polarized light beam is incident upon the surface to produce a polarized light exposure having a substantially uniform direction of polarization across the surface.  
     
     
       28. The method of  claim 27 , wherein the surface comprises a surface of an optical compensation film. 
     
     
       29. The method of  claim 27 , wherein the surface comprises a surface of a liquid crystal cell.